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Open Access Theses & Dissertations

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Articles 31 - 60 of 113

Full-Text Articles in Physics

Self-Interaction Corrected Polarizabilities Of Small Molecules, Sharmin Akter Jan 2017

Self-Interaction Corrected Polarizabilities Of Small Molecules, Sharmin Akter

Open Access Theses & Dissertations

Density Functional Theory (DFT) is one of the most successful and popular computational Quantum Mechanical approaches to understand materials. DFT allows the prediction of material properties from the electron density. Although in principle density functional theory is exact, it, however, relies on approximate functional for exchange-correlation energy. Due to the approximate nature of the exchange-correlation functional, the self-Coulomb energy of the electrons is not exactly canceled out by the self-exchange leading the spurious self-interaction error (SIE). This error is responsible for the unphysical orbital energies of DFT and delocalization of the orbitals. The orbital energies of the valence electrons are ...


Studies Of Direct Solar Irradiance And Aerosol Optical Depth Using An Mfrsr And A Microtop Sunphotometer In The El Paso-Juarez Airshed, Arjun Aryal Jan 2017

Studies Of Direct Solar Irradiance And Aerosol Optical Depth Using An Mfrsr And A Microtop Sunphotometer In The El Paso-Juarez Airshed, Arjun Aryal

Open Access Theses & Dissertations

The study of Solar Irradiance and Aerosol Optical Depth (AOD) plays an important role in understanding the regional and global climate distribution, and is also important in air pollution studies. In this work an MFRSR (Multi-Filter Rotating Shadowband Radiometer) and a Portable Microtop Sunphotometer were used to measure irradiances and to obtain optical depth values for the El Paso-Juarez Airshed. The Langley method applied on the MFRSR irradiance data was used to calculate the AOD values. The spatial distribution of AOD for this region was obtained using a Microtop Sunphotometer. The graphs were generated using GIS Shapefiles. In addition, the ...


Electronic Structure Studies On Transition Metal Containing Endohedral Fullerenes, Carbon Onions And Zinc Sulfide Cages, Shusil Bhusal Jan 2017

Electronic Structure Studies On Transition Metal Containing Endohedral Fullerenes, Carbon Onions And Zinc Sulfide Cages, Shusil Bhusal

Open Access Theses & Dissertations

We present the most stable structures for VXSc3-XN@C2n (where X=1-3 and 2n=70, 76, 78 and 80) using a systematic procedure that involves all possible isomers of the host fullerene cages. Subsequently, a detailed investigation of structural and electronic properties of the lowest energy isomers is performed using density functional theory in combination with large polarized Gaussian basis sets. The search procedure developed involved structural optimizations of thousands of fullerenes and correctly identifies the experimentally observed VSc2N@C80 and V2ScN@C80 isomer as the most stable structures. The structural analysis shows that a few V-doped endohedral fullerenes do ...


Spectroscopic And Microscopic Analysis Of Graphene For Sensor Applications, Tamanna Tasneem Khan Jan 2017

Spectroscopic And Microscopic Analysis Of Graphene For Sensor Applications, Tamanna Tasneem Khan

Open Access Theses & Dissertations

As a two-dimensional material, graphene shows very good thermal and electrical conductivities, which, with its unique optical properties, makes it suitable for a variety of applications. In this study, we present detailed investigations by confocal Raman and Drude model analysis of the material's changes and improvements, as it transitioned from 3D graphite to 2D graphene. Besides Raman spectral recording, which can detect single, a few, and multi-layers of graphene, confocal Raman mapping allows distinction of such domains and direct visualization of material inhomogeneity. Moreover, far-infrared transmittance measurements, which are related to electrical conductivity, demonstrate a distinct increase of conductivity ...


Ac Susceptibility And Epr Investigations Of Superspin Dynamics In Manganese Oxide Nanoparticles, Mahesh Koirala Jan 2017

Ac Susceptibility And Epr Investigations Of Superspin Dynamics In Manganese Oxide Nanoparticles, Mahesh Koirala

Open Access Theses & Dissertations

We have investigated the superspin dynamics of 5 nm and 10 nm mixed state Mn3O4 nanoparticles utilizing ac-susceptibility and electron paramagnetic resonance measurements. The out of phase component of the ac-susceptibility measurements show a magnetic anomaly below (T


Study Of Electron Gas On A Neutron-Rich Nuclear Pasta, Enrique Ramirez-Homs Jan 2017

Study Of Electron Gas On A Neutron-Rich Nuclear Pasta, Enrique Ramirez-Homs

Open Access Theses & Dissertations

This study used a classical molecular dynamics model to observe the role of electron gas on the formation of nuclear structures at subsaturation densities (Ï?<0.015 fm^-3) and low temperatures (T< 1MeV ). The simulations were performed by varying the Coulomb interaction strength on systems of isospin symmetric and asymmetric matter with periodic boundary conditions. The effect was quantified on the fragment size multiplicity, the inter-particle distance, the isospin content of the clusters, the nucleon mobility and cluster persistence, and on the nuclear structure shapes. The existence of the nuclear pasta structures was observed even with the absence of the Coulomb interaction but with a modication of the shapes formed. It was found that the presence of the electron gas tends to distribute matter more evenly, forms less compact objects, decreases the isospin content of clusters, modies the nucleon mobility, reduces the persistence and the fragment size multiplicity, but does not alter the inter-particle distance in clusters. The degree of these effects also varied on the nuclear structures and depended on their isospin content, temperature, and density.


Time Degradation Of Perovskites, Nazia Sharmin Jan 2017

Time Degradation Of Perovskites, Nazia Sharmin

Open Access Theses & Dissertations

Perovskite organic-inorganic compounds are of interest for photovoltaic purposes, unfortunately, some of the organic-inorganic elements tend to evaporate rather rapidly rendering the films less effective for photoelectric use. In this study, we examine the evaporation of Perovskite organic-inorganic compounds produced by several manufacturing techniques. In particular we perform XRF and XPS inspections as a function of time and determine the fabrication method that best conserves iodine and lead.


Raman Microscopic Analysis Of Internal Stress In Boron-Doped Diamond Thin Films, Emma M.A. Sundin Jan 2017

Raman Microscopic Analysis Of Internal Stress In Boron-Doped Diamond Thin Films, Emma M.A. Sundin

Open Access Theses & Dissertations

The correlations between induced stress on undoped and boron-doped diamond (BDD) thin films, sample chemical composition, and fabrication substrate are investigated in this study via confocal Raman microspectroscopic analysis. Stability of BDD films is relevant to fast-scan cyclic voltammetry, as film delamination and dislocation of BDD-coated electrodes that can occur during neurosurgical electrode implantation can negatively impact the biosensing reliability of this technique. Electrodes were fabricated by coating cylindrical tungsten rods using a custom-built chemical vapor deposition reactor. The results of the analysis reveal a direct correlation between regions of pure diamond and enhanced material stress, as well as preferential ...


Neutrino Oscillations And The Reno Experiment, Karla Rosita Tellez Giron Flores Jan 2017

Neutrino Oscillations And The Reno Experiment, Karla Rosita Tellez Giron Flores

Open Access Theses & Dissertations

Neutrinos are the second most common particles in the universe, after the photons. Neutrinos (and antineutrinos) exist in three different "flavors", namely, electron, tau and muon neutrinos. A physical neutrino, however, can oscillate among these three flavors and, thus, it is said to be a mix of the three flavor states. In quantum mechanics representation, it is said that the three flavor states are the mixture of the three mass states. This mixture of neutrinos can generally be parameterized by the three so-called mixing angles (&thetas;12, &thetas;23, &thetas;13), three squared mass differences Δmij 2, i, j = 1, 2, 3 and ...


Spectroscopic Analysis Of Neurotransmitters: A Theoretical And Experimental Raman Study, Matthew Alonzo Jan 2017

Spectroscopic Analysis Of Neurotransmitters: A Theoretical And Experimental Raman Study, Matthew Alonzo

Open Access Theses & Dissertations

Surface-enhanced Raman spectroscopy (SERS) was applied to investigate the feasibility in the detection and monitoring of the dopamine (DA) neurotransmitter adsorbed onto silver nanoparticles (Ag NPs) at 10-11 molar, a concentration far below physiological levels. In addition, density functional theory (DFT) calculations were obtained with the Gaussian-09 analytical suite software to generate the theoretical molecular configuration of DA in its neutral, cationic, anionic, and dopaminequinone states for the conversion of computer-simulated Raman spectra. Comparison of theoretical and experimental results show good agreement and imply the presence of dopamine in all of its molecular forms in the experimental setting. The dominant ...


Label-Free Raman Imaging To Monitor Breast Tumor Signatures, John Ciubuc Jan 2017

Label-Free Raman Imaging To Monitor Breast Tumor Signatures, John Ciubuc

Open Access Theses & Dissertations

Methods built on Raman spectroscopy have shown major potential in describing and discriminating between malignant and benign specimens. Accurate, real-time medical diagnosis benefits in substantial improvements through this vibrational optical method. Not only is acquisition of data possible in milliseconds and analysis in minutes, Raman allows concurrent detection and monitoring of all biological components. Besides validating a significant Raman signature distinction between non-tumorigenic (MCF-10A) and tumorigenic (MCF-7) breast epithelial cells, this study reveals a label-free method to assess overexpression of epidermal growth factor receptors (EGFR) in tumor cells. EGFR overexpression sires Raman features associated with phosphorylated threonine and serine, and ...


Methods For Producing Graphene From Petroleum By-Products, Eva M. Deemer Jan 2017

Methods For Producing Graphene From Petroleum By-Products, Eva M. Deemer

Open Access Theses & Dissertations

N/A


Bragg Gratings In Polarization Maintaining Optical Fiber As Three Dimensional Strain Sensor, Joel Quintana Jan 2017

Bragg Gratings In Polarization Maintaining Optical Fiber As Three Dimensional Strain Sensor, Joel Quintana

Open Access Theses & Dissertations

Fiber-Bragg Gratings (FBG) for Structural Health Monitoring (SHM) have been studied extensively as they offer electrically passive operation, electromagnetic interference (EMI) immunity, high sensitivity and multiplexing as compared to conventional electric strain sensors. FBG sensors written within polarization maintaining (PM) optical fiber offer ad- ditional dimensions of strain measurement, greatly reducing the number of sensors needed to properly monitor a structure. This reduction however, adds complexity to the dis- crimination of the sensorâ??s optical response to its corresponding applied strains. This Dissertation defines the set of algorithms needed to measure planar strain using PM-FBGs exclusively. It defines the minimum ...


Using Underground Radon To Detect Inactive Geological Faults, Germán Rodríguez Ortiz Jan 2017

Using Underground Radon To Detect Inactive Geological Faults, Germán Rodríguez Ortiz

Open Access Theses & Dissertations

This Thesis presents the results of an investigation of the concentration of radon in soil around a fault in the East Franklin Mountains in the El Paso area in West Texas. The connection between underground radon exhalations near active faults has been known for decades, but possible similar increases of underground radon levels around inactive faults have not been studied as thoroughly. Arguing that the dilatancy-diffusion model used to explain the phenomenon near active faults does not apply to the case of inactive faults, a hypoThesis is formulated under which increased levels of underground radon must be present near inactive ...


Structural Modifications In The Rbxcs1-Xpo 4 (0 ≤ X ≤ 1) Superprotonic Conductor Series: A Single-Crystal X-Ray Diffraction And Impedance Spectroscopy Study, Andres Jose Encerrado Manriquez Jan 2017

Structural Modifications In The Rbxcs1-Xpo 4 (0 ≤ X ≤ 1) Superprotonic Conductor Series: A Single-Crystal X-Ray Diffraction And Impedance Spectroscopy Study, Andres Jose Encerrado Manriquez

Open Access Theses & Dissertations

We have used single-crystal X-ray diffraction measurements to investigate the structural modifications induced by Rb-doping of the protonic conductor CsH2PO4. Data collected on the RbxCs 1-xH2PO4 (0 ≤ x ≤ 1) series shows that the monoclinic P21/m CsH2PO4 presentation persists upon Rb-doping up until x = 0.8. Rb0.8Cs0.2H2PO 4 exhibits a previously unreported P21/c monoclinic structure, where the mirror plane is lost and disorder is present in the PO4 tetrahedra even at room temperature. Higher levels of x display a tetragonal I-42d unit cell isomorphic with the known structure of RbH2PO 4. The temperature dependence of the proton ...


Dft Study Of Adsorption Of Trimetallic Endohedral Fullerenes On Graphene, Nakul Nitin Karle Jan 2017

Dft Study Of Adsorption Of Trimetallic Endohedral Fullerenes On Graphene, Nakul Nitin Karle

Open Access Theses & Dissertations

A density functional theory (DFT) study on the geometric and electronic structure of C60 and Sc3N@C80 along with their adsorption on pristine single layer graphene (SLG) is presented. C60 is found to adsorb in two nearly degenerate configurations: (i) with a pentagon facing the SLG, which is the most stable one, and (ii) with a hexagon facing the SLG in a face-to-face perfect alignment, rarely common in Ï?â??Ï? interactions, 0.06 eV higher in energy. The calculated binding energy of 0.76 eV, which includes dispersion effects, is in good agreement with previous theoretical and experimental reports ...


Studying Grazing Behavior Of Cafeteria Roenbergensis With Two-Photon Microscopy, Faisal Abedin Abedin Jan 2016

Studying Grazing Behavior Of Cafeteria Roenbergensis With Two-Photon Microscopy, Faisal Abedin Abedin

Open Access Theses & Dissertations

Major innovations in recent years have largely revolutionized the fluorescence imaging. Two-photon fluorescence microscopy is one of them. Two photon fluorescence microscopy has evolved as an alternative to conventional single-photon confocal microscopy and has been shown to provide several advantages. These include three-dimensionally resolved fluorescence imaging of living cells deep within thick, strongly scattering samples, and reduced phototoxicity, enabling long term imaging of photosensitive biological specimens. The inherent three-dimensional resolution of TPE microscopy has been exploited in a number of studies wherein spatial discrimination of fluorescence signals at the micrometer and submicrometer scale within thick biological specimens proved critical. In ...


Two-Photon Excitation Based Photochemistry And Neural Imaging, Kevin Andrew Hatch Jan 2016

Two-Photon Excitation Based Photochemistry And Neural Imaging, Kevin Andrew Hatch

Open Access Theses & Dissertations

Two-photon microscopy is a fluorescence imaging technique which provides distinct advantages in three-dimensional cellular and molecular imaging. The benefits of this technology may extend beyond imaging capabilities through exploitation of the quantum processes responsible for fluorescent events. This study utilized a two-photon microscope to investigate a synthetic photoreactive collagen peptidomimetic, which may serve as a potential material for tissue engineering using the techniques of two-photon photolysis and two-photon polymerization. The combination of these techniques could potentially be used to produce a scaffold for the vascularization of engineered three-dimensional tissues in vitro to address the current limitations of tissue engineering. Additionally ...


Innovations In Thermoelectric Materials Research: Compound Agglomeration, Testing And Preselection, Hugo Lopez Jan 2016

Innovations In Thermoelectric Materials Research: Compound Agglomeration, Testing And Preselection, Hugo Lopez

Open Access Theses & Dissertations

Thermoelectric materials have the capacity to convert a temperature differential into electrical power and vice versa. They will represent the next revolution in alternative energies once their efficiencies are enhanced so they can complement other forms of green energies that depend on sources other than a temperature differential.

Progress in materials science depends on the ability to discover new materials to eventually understand them and to finally improve their properties. The work presented here is aimed at dynamizing the screening of materials of thermoelectric interest. The results of this project will enable: theoretical preselection of thermoelectric compounds based on their ...


Study On Dioxygen Binding To Heme Using Scan Functional, Zegnet Yimer Muhammed Jan 2016

Study On Dioxygen Binding To Heme Using Scan Functional, Zegnet Yimer Muhammed

Open Access Theses & Dissertations

Density functional theory, a quantum mechanical based electronic structure method with GGA-PBE and MGG-SCAN functionals, are used to investigate the structure and energies of singlet, triplet, and quintet spin states of FeP (iron Porphyrin), FePIm (imidazole iron porphyrin), and FePImO2 (dioxygen imidazole iron porphyrin) systems. The binding and release of dioxygen to and from hemoglobin (Hb) are the most crucial reaction takes place in human body to sustain the existence of life. FePImO2 is used to model this phenomenon. When O2 binds to FePIm, the system undergoes a conformational change. i.e. from domed structure of FePIm in which the ...


Sparse Matrix Diagonalization In The Nrlmol Electronic Structure Code, Md Mahmudulla Hassan Jan 2016

Sparse Matrix Diagonalization In The Nrlmol Electronic Structure Code, Md Mahmudulla Hassan

Open Access Theses & Dissertations

Density functional theory (DFT) based simulations are playing a major role in quantum mechanical studies of materials ranging from molecules, nanoparticles to the biological systems as they offer insights that are not directly accessible from experiments and also due to their ability to make sufficiently accurate predictions. The DFT implementation in the NRLMOL electronic structure code employs Gaussian basis sets to express the Kohn-Sham orbitals. A major computationally demanding task in the electronic structure calculations is solution of the generalized eigenvalue problem, that is the determination of nontrivial solutions (λ, c) of Hc = λOc where H and O are the ...


Density Functional Study Of Reactivity And Regioselectivity Of H2o@C60, Govinda Bahadur Kc Jan 2016

Density Functional Study Of Reactivity And Regioselectivity Of H2o@C60, Govinda Bahadur Kc

Open Access Theses & Dissertations

The exohedral reactivity of endohedral fullerene has aroused significant interest because of its potential applications in biology, medicine and material science. The encapsulation of a single water molecule without any hydrogen bonding to other compounds, inside the hydrophobic environment of C60 is an intriguing topic to study about. In 2011, Kurotobi and Murata successfully synthesized H2O@C60 fullerene. The presence of a polar water molecule inside the cage is expected to cause changes in the exohedral reactivity of C60. In order to find out the impact of an entrapped single water molecule on the reactivity of C60 fullerene, we use ...


Scalability Improvements To Nrlmol For Dft Calculations Of Large Molecules, Carlos Manuel Diaz Jan 2016

Scalability Improvements To Nrlmol For Dft Calculations Of Large Molecules, Carlos Manuel Diaz

Open Access Theses & Dissertations

Advances in high performance computing (HPC) have provided a way to treat large, computationally demanding tasks using thousands of processors. With the development of more powerful HPC architectures, the need to create efficient and scalable code has grown more important. Electronic structure calculations are valuable in understanding experimental observations and are routinely used for new materials predictions. For the electronic structure calculations, the memory and computation time are proportional to the number of atoms. Memory requirements for these calculations scale as N2, where N is the number of atoms. While the recent advances in HPC offer platforms with large numbers ...


Complex Gleason Measures And The Nemytsky Operator, Miguel Angel Valles Jan 2016

Complex Gleason Measures And The Nemytsky Operator, Miguel Angel Valles

Open Access Theses & Dissertations

This Thesis is devoted to generalize previous results on Gleason measures

to complex Gleason measures, and to develop a functional calculus

for complex measures in relation to the Nemytsky operator. Furthermore

we present the interpretation of our results in the field of quantum

mechanics, some concrete examples and further extensions of several

theorems.


Dft Study On The Structure And Properties Of Vsc2n@C68, Surendra Bhatta Jan 2016

Dft Study On The Structure And Properties Of Vsc2n@C68, Surendra Bhatta

Open Access Theses & Dissertations

A computational study on the structure and electronic properties of the VSc2N@C68 molecule was carried out using the density functional theory. This molecule is based on the recent report on the synThesis of the VSc2N@C80 and V2ScN@C80 fullerenes. The Sc3N@C68 is also a stable endohedral fullerene that has a cage with fuse pentagonal rings. The doping by a V atom changes the structure as well as the spin state of the Sc3N@C68 from S=0 to S=1 state. Since the C68 has 6332 isomers, we have carried out an extensive search for the lowest ...


Equation Of State Of A Dense And Magnetized Neutron System, Md Masud Jan 2016

Equation Of State Of A Dense And Magnetized Neutron System, Md Masud

Open Access Theses & Dissertations

Neutron stars (NSs) are the windows to check the validation of physical laws at extreme conditions, for example, at very high densities and strong magnetic fields and thus to reach the equations of state (EoS) for a better understanding of the structure as well as the composition of the NSs. In our investigations, it is found that the system's (NSs) pressure becomes anisotropic due to the breaking of rotational symmetry in the presence of strong magnetic fields, which even can be significantly sufficient to lead into the deformation of NSs or to destroy itself.


Educational Use Of Social Media: Exploring Science And Engineering College Students' Perceptions About Utilizing Facebook To Enhance The Learning Of Physics, Angel Salvador Marquez Jan 2016

Educational Use Of Social Media: Exploring Science And Engineering College Students' Perceptions About Utilizing Facebook To Enhance The Learning Of Physics, Angel Salvador Marquez

Open Access Theses & Dissertations

The aim of this qualitative investigation is to explore a group of science and engineering students' perceptions about utilizing Facebook to enhance the learning of physics. Particularly, a survey composed of multiple choice and open-ended questions was employed as to obtain participantsâ?? reactions on a proposed scenario where Facebook is utilized in an Introductory Classical Mechanics course as the medium to manage the following academic activities throughout the semester: examinations, class preparations, study guides, homework assignments, lab preparations, creating group studies, and class participation dynamics. Out of the 120 potential candidates, 106 of them accepted to voluntarily participate in this ...


Molecular Dynamics Study On Defect Reduction Strategies Towards The Fabrication Of High Performance Cd1-Xznxte/Cds Solar Cells, Jose Juan Chavez Jan 2015

Molecular Dynamics Study On Defect Reduction Strategies Towards The Fabrication Of High Performance Cd1-Xznxte/Cds Solar Cells, Jose Juan Chavez

Open Access Theses & Dissertations

Cadmium Telluride is a material widely used in terrestrial thin film photovoltaic applications due to its nearly ideal band gap (~1.5 eV) and high absorption coefficient. Due to its low manufacturing cost, this technology has the potential to become a significant energy resource if higher energy conversion efficiencies are achieved. However, the module efficiencies (~14%) are still far from the theoretical maximum (~30%) for this material in a single junction configuration. The reason behind this low performance is attributed to the high number of defects that are present within the device materials. The physics behind the formation mechanisms of ...


The Meteorological Conditions Affecting The Propagation Of Respiratory Diseases, Rosette Maria Gonzalez Jan 2015

The Meteorological Conditions Affecting The Propagation Of Respiratory Diseases, Rosette Maria Gonzalez

Open Access Theses & Dissertations

Valley Fever, also known as Coccidioidomycosis, is endemic of the US Southwest. In 2012 this disease was the second most-reported disease in Arizona, according to the New Yorker January 2014 edition. The Paso Del Norte Region (PdN) is a semi-arid region with significant agricultural acreage and Valley Fever is known to be a threat in this region. It is our goal in this Thesis work to apply an existing PBL Height Program (e.g., Liu, et.al.) to the Paso Del Norte Region (PdN) to study the effect it has in the transmission of Valley Fever. Obtaining the PBLH as ...


Ac-Susceptibility And Epr Investigations Of Superspin Dynamics In Magnetite Nanoparticles, Alex D. Price Jan 2015

Ac-Susceptibility And Epr Investigations Of Superspin Dynamics In Magnetite Nanoparticles, Alex D. Price

Open Access Theses & Dissertations

In this investigation we use two complementary techniques to distinguish between superparamagnetic blocking (SPB) and superspin-glass (SSG) freezing phenomena in magnetite nanoparticles. While these manifestations of the superspin dynamics are fundamentally different, they have similar "signatures", especially in dc-magnetization experiments. Even if ac-susceptibility measurements are employed, careful use of mathematical models to analyze the data are needed to uncover which type of phenomena (SPB or SSG freezing) occurs within the material. Yet, by utilizing electron paramagnetic resonance (EPR) on a 10 nm Fe3O4 nano-powder as well as on a ferrofluid (based on the same nanoparticle ensemble) we found a very ...